The present invention relates to a washing machine including an improved apparatus for cleaning a recirculating filter of the machine, and to such apparatus for use in a washing machine.
More particularly, the present invention relates to such an improved washing machine and apparatus wherein a recirculating filter, for filtering impurities from water recirculated during a recirculating or washing phase of operation of the machine, is automatically cleaned at the end of each operating cycle of the machine.
British Pat. No. 2,204,482 discloses a dishwashing machine including a washing tub having at the bottom thereof a water collecting sump, a rotary spray arm mounted within the tub above the sump, a recirculating pump recirculating water from the sump through the rotary spray arm, and a fine-mesh recirculating filter disposed in the tub in the path of water between the rotary spray arm and the recirculating pump. The recirculating filter includes a substantially or relatively flat portion positioned between the rotary spray arm and the sump and having an opening directly connecting the interior of the tub to the intake of a drain pump that is operated during a drain phase of operation of the washing machine to drain water from the tub. The recirculating filter also includes a substantially cylindrical or frustoconical portion surrounding the opening in the substantially flat portion and extending downwardly therefrom. The two portions of the filter are substantially concentric with respect to the axis of rotation of the rotary spray arm, and the rotary spray arm is capable of directing toward the filter at least one jet of water substantially tangentially to the surface of the filter that lies upstream with respect to the path of water flow. This arrangement, that preferably includes one water jet tangential to the flat portion of the filter and another water jet tangential to the cylindrical portion of the filter, is advantageous in that it enables particles of dirt or impurities which are retained by the entire surface of the recirculating filter to be passed automatically toward the drain during operation of the recirculating pump. However, the intake of the drain pump is substantially separate from the inlet of the recirculating pump. As a result, during the drain phase of operation of the machine, any water collected at the bottom of the sump cannot be entirely withdrawn or evacuated from the sump. This particularly is true with regard to any such water at the bottom of the sump adjacent the inlet of the recirculating pump. This water becomes progressively dirtier, and it is desirable that such water be evacuated from the sump during the drain phase of operation of the machine.
A system for evacuating such residual soiled water collected at the bottom of the sump and adjacent the hydraulic recirculation circuit is disclosed in Italian No. 1,187,294 wherein there is shown a dishwashing machine in which the intakes or inlets of the recirculating and drain pumps are connected to one another by a conduit having a first portion extending from the intake of the drain pump upwardly and a second portion extending downwardly to a level which is adjacent to but higher than the bottom of the water collecting sump. The hydrostatic and hydrodynamic characteristics of the hydraulic circuit are such that an effective connection between the two intakes or inlets of the pumps occurs only when the drain pump is in operation. Accordingly, it is the drain pump which is operated to discharge residual soiled water collected at the bottom of the sump, i.e. at the bottom of the recirculation circuit. However, to ensure that this system operates it is necessary that the hydrostatic and hydrodynamic characteristics of the hydraulic circuit be controlled very accurately. This however is not possible to achieve at all times, and as a result this system is unsatisfactory. Furthermore, upon the occurrence of an accidental malfunction of the hydraulic circuit, there will be provided a direct connection established, for the duration of the remaining part of the operating or washing cycle of the machine, between the water discharge portion of the machine and the washing or recirculating section thereof. Upon such an occurrence, the washing or recirculating operation will be carried out by soiled or dirtied water, and this results in the entire washing machine not functioning properly.
Italian Pat. No. 952,947 discloses a dishwashing machine provided with a single pump capable of feeding water drawn in from the collecting sump alternately to the rotary spray arm and to an ejector associated with a drain hose of the machine. The ejector is provided with a branch pipe terminating in a nozzle extending toward a conical portion of the recirculating filter, so that during the drain phases of operation of the machine the pump discharges water and the conical portion of the recirculating filter is partially cleaned by a water jet discharged from the nozzle. In practice however, this system is unsatisfactory. For example, the delivery of the pump is connected with the water recirculation and the water discharge or drain circuits through respective solenoid valves that have to be selectively and alternately opened and closed to perform the various phases of circulation and discharge of water. Due to the necessity of provision of these solenoid valves, that are notoriously unreliable, and the respective control devices therefor, the washing machine as a result becomes undesirably complicated. Furthermore, the entire drain system is scarcely effective in operation, particularly with regard to the final phases of drainage of residual water from the wash tub, since the water flows provided both by the ejector and by the nozzle are variable, that is such flows decrease with a decreasing level of residual water.